2006年 Structure Analysis of Polymer Electrolyte membrane for Fuel Cell Using Positron Annihilation Spectroscopy 5th 21COE International Symposium Towards creating new industries based on inter-nanoscience, Y. Akiyama, Y. Shibahara, N. Kimura, S. Tagawa, S. Takeda, Y. Izumi, Y. Honda, and S. Nishijima